Validate your solar data with 3E’s Solar Sensor Check


When we talk about solar power generation, solar radiation is defined as the primary resource and, thus, the reference for almost any analysis. On-site measurements of irradiance serve as a reference for resource assessment, provisional and final plant commissioning, and performance reporting for asset management.

However, when reviewing pyranometers and silicon reference cells in the field, we find that both of these measurements tend to underestimate the solar resource. 3E has identified this phenomenon by analyzing data from a random selection of 88 sensors recorded by SynaptiQ, its performance monitoring tool. The reference for the comparison was 3E’s satellite irradiation service, which has proven to have a very low error for annual irradiation. The results show that 50% of all sensors tend to underestimate the yearly irradiation by 7% or more. We can therefore conclude that many resource assessments or PR calculations based on these sensors and data will be biased in the same way.

Figure: Average sensor irradiation over satellite irradiation for 88 sensors in Europe; the dot size represents the size of the PV plant where the sensor is installed.

The causes for these deviations are multiple: data gaps, bad mounting, shadowing, soiling and sensor degradation. In order to surpass this bias, 3E is now offering a Solar Sensor Check, to identify these root causes of bad sensor performance. The figure below shows an example of a sensor with wrong azimuth and tilt. A PR evaluation based on this sensor is meaningless. The Solar Sensor Check shows how the sensor is really mounted, thus how the error can be easily corrected and meaningful analyses conducted.

Example: nominal orientation as configured in SynaptiQ and best fit orientation; the Best fit values indicate how the sensor is really mounted.

3E is currently developing a series of data mining services to better assess operational performance. The Solar Sensor Check is one of them.

The Solar Sensor Check is offered for meteo stations as well as for operational plants.


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